A homicide bomber, disguised as an Orthodox Jew, blew himself up on a bus packed with young parents and kids coming home from prayers in Jerusalem last night, killing at least 18 and injuring scores.

At least one New Yorker – a 50-year-old Rockland County woman – was among the dead, a source told The Post.

At least five children were killed – including babies still wearing their diapers as their corpses were bundled into white body bags.

A month-old infant was fighting for his life after his broken body was discovered beneath a corpse in the twisted, scorching wreckage.

Israeli hospital officials hit the national airwaves in a heart-wrenching appeal to try to find the infant’s missing parents, as well as those of a tragic 18-month-old girl who had already died on a respirator, and another badly hurt child.

Some feared the worst: that the children’s moms and dads might already be among the dead.

“There were small babies bleeding on the ground. One of our workers was leaning over an infant, no more than 15 months old, giving mouth-to-mouth resuscitation,” said a shaken Zelig Feiner, an official with an Orthodox burial society.

“It was hopeless.”

In addition to the New York woman, authorities were checking reports of two other Americans killed.

A wounded man told Israeli TV that as soon as the explosion occurred, “children flew out of the bus.”

Zvi Weiss, an 18-year-old Jewish seminary student from New York City, said he was sitting in the front of the bus when the bomb went off, and “everything went black.

“I climbed out of the broken window and started running. All around me there were people covered in blood, screaming, some with limbs missing,” Weiss said.

The double-long bus’ passengers also reportedly included members of one family that had just celebrated a Bar Mitzvah at the Western Wall, Judaism’s holiest site.

In a twist of fate, another group of young boys attending the party tried to board the bus, too – but were turned away because it was too crowded.

“The driver did not even open the doors for them. This saved their lives,” Pinchas Kramer, whose son was among those who had been turned away, told a local newspaper.

The us was returning from the wall at around 9:15 p.m. when it exploded just outside the densely populated Orthodox quarter of Shmuel Hanavi in the city’s center.

The bomber is believed to have boarded the bus dressed in the dark, traditional garb of ultra-Orthodox Jews, which enabled him to blend in with the crowd, Israeli officials said.

He was identified as 29-year-old Raed Abdul Hamid Mask, a married high-school teacher and father of two from Hebron who doubled as a member of the Hamas terror group.

After the attack, Hamas released a chilling videotape of Mask in which the self-described “sheik” vowed to avenge a Hamas leader’s recent death.

The killer spewed his venom-filled speech while holding a rifle in one hand and the Koran in the other.

“You have to remember the target of the attack, a moving bus bringing families who had been praying at the Western Wall,” government spokesman Dore Gold said.

The bomber had apparently packed his explosives belt with metal pellets and shards to maximize the number of casualties, Israeli officials said.

He moved quietly to the middle of the bus before detonating his deadly package, they said.

Barry Moody, a Reuters reporter who was standing near the bus when it exploded, recalled seeing “dismembered bodies, including a severed arm, a severed lower torso and a woman with her chest blown out.”

Rescuers with blow torches rushed in to try to pry the screaming wounded from the burning wreckage, as small, bloodied children wandered through the site in shock and loud sobs and wails from adult survivors filled the air.

Jacob Bitnovsky, who was driving his car nearby when the bombing occurred, said that as soon as he heard the blast, “I got out of the car and ran.

“I saw a child on the ground gasping for air,” he said.

At least 40 children were among the more than 136 injured.

The attack was the worst on Israeli soil in more than a year – and immediately threw into doubt ongoing talks over the region’s proposed “road map” to peace.

There were conflicting claims of responsibility last night.

In addition to Hamas, Islamic Jihad said it had carried out the attack, the worst single bombing in Israel since June 18, 2002, when a bomber blew himself up on a crowded bus in Jerusalem, killing 19.

“As long as there are Israeli violations to the truce, Israel will remain responsible for the consequences,” Hamas leader Ismail Abu Shanab said yesterday.

The Palestinian Authority, struggling to keep peace negotiations alive, cut off dialogue with Islamic Jihad and Hamas while also vowing to take action against the groups. It did not elaborate.

Meanwhile, at a Palestinian refugee camp in Lebanon, hundreds of cheering young men openly passed out sweets in the street to “celebrate” the attack.

“Death to America! Death to Israel!” the protesters yelled.

Israel immediately froze talks on the handover of four key West Bank towns to the Palestinians.